Age at Diagnosis of Neurofibromatosis 1: An Audit of Practice

Neurofibromatosis 1 (NF1) is a common genetic disease with an incidence of about 1 in 2,500, an autosomal dominant mode of inheritance and a high rate of new mutations. Two striking aspects of NF1 are its progression with age and its extreme variability. Its diagnosis is based on 7 criteria of which 2 are required for diagnosis: significant cafe-au-lait macules (CLM), neurofibromas of any type or 1 plexiform neurofibroma, freckling in the axillary or inguinal regions, optic glioma, Lisch nodules, a distinctive osseous lesion such as sphenoid dysplasia or thinning of the long bone cortex with or without pseudarthrosis, a first-degree relative with NF1. Although specificity and sensitivity of these criteria are high during adulthood, their sensitivity is low during early childhood: 97% of NF1 patients meet them by the age of 8 years, but only 70% by the age of 1 year. In France, the diagnosis is often made in young adults, and the detection of the early complications needs precocious diagnosis . We conducted a retrospective audit of practice to identify features associated with early diagnosis.